StarPlot Documentation

0. Guided Tour of StarPlot

The first thing to know about StarPlot is its purpose. The
main goal of StarPlot is to show the spatial relationships between
different star systems, not to display a realistic simulation of how
they would actually look when seen in space. For that, you may want
to try the much more ambitious program Celestia by Chris Laurel.
Think of StarPlot as a road map and Celestia as the actual landscape.
That said, you might find a guided tour of StarPlot useful to
see what it can do.

0.1. Getting Started

0.1.1. For a generic UNIX-like operating system

I assume you have already installed StarPlot
itself. You will need to install the Gliese and Yale sets of
star data for this tour. From the StarPlot data file web page
(http://starplot.org/datafiles.html), download the
"Third Catalogue of Nearby Stars for StarPlot 0.95" (often called
the Gliese Catalog) and the
"Yale Bright Star Catalog for StarPlot 0.95."

Once you've downloaded them, open up an xterm (or other terminal)
and run the commands

starpkg yale5-0.95.tar.gz ; starpkg gliese3-0.95.tar.gz

to convert the data files to StarPlot format. This will create the
files "gliese3.stars" and "yale5.stars" in your
current directory. (In the future, StarPlot will include a graphical
dialog box from which you will be able to download and install data
files automatically.) You should move these files into the directory
/usr/local/share/starplot, where it will be
easier to find them from StarPlot's file opening dialog. (You will
probably need to log in as root to move the files there.)

0.1.2. For Debian GNU/Linux

The distributor of your operating system may also have packaged
the Gliese and Yale catalogs already. If you are using Debian
GNU/Linux, for instance, instead of following the above steps
you can simply run

apt-get install starplot gliese yale
apt-get install stardata-common

while logged in as root. Your /etc/apt/sources.list file
will need to include the non-free section. Note that the
stardata-common package is present only in the "etch",
"lenny" and
"sid" versions of Debian; if you have an earlier version of Debian
("sarge" or "woody"), don't run the second command above. The catalogs
in StarPlot format will be automatically generated for you
in the /usr/share/starplot directory. In this case they
will be named gliese.stars and yale.stars (without
any digits in the names).

0.1.3. For Fedora Linux

If you are using Fedora Linux (version 7 or newer), you can install
StarPlot and the data packages by running

while logged in as root. The catalogs
in StarPlot format will be automatically generated for you
in the /usr/share/starplot directory. The files
will be named gliese3.stars and yale5.stars.
The file stars_with_planets3.stars from the starplot-contrib
package is a set of stars known to have planets, contributed by
Vince Barwinski. (Non-Fedora users may obtain this catalog
from the StarPlot
data files web page.)

0.2. Exploring Our Stellar Neighborhood

Go ahead and run StarPlot by entering the command

starplot &

(you may also be able to run StarPlot from a menu entry on your
desktop if one exists). Then, in the StarPlot main window, select
the "File->Open Star Database" menu option and choose the
file gliese.stars or gliese3.stars (whichever
exists on your system).

You can also save a step by telling StarPlot to open the correct
file at the command line. For instance, supposing that the
Gliese catalog is named gliese3.stars and is in your
current directory, you would type

starplot ./gliese3.stars &

However you started StarPlot, you should now be at a screen that looks
a lot like this:

The Sun is at the center of the chart, and some of the nearest
stars, those within 10 light-years of us, are shown. (A light-year
is the distance that a beam of light travels in one year. The
distances in interstellar space are almost incomprehensibly vast!)
You've probably heard of Alpha Centauri (the nearest star system) and
Sirius (the star that appears brightest in our sky). The other
stars are dim red dwarfs unfamiliar to most people. The color of
the dots representing stars is roughly the same as their actual color
in the sky: hot stars are blue and cool stars are red, while stars
having a temperature similar to our Sun are shown in yellow.
The relative sizes of the dots represent the stars' brightnesses.

If you want to view the star chart from a different angle, this
is as simple as clicking on the four buttons in the button bar at
left with arrows on them. At any point, if you find a view you
like, you can save it as an image (PNG format) from the
"File->Save Chart as PNG" menu option.

Let's zoom out a bit. Click the button at the upper left of the
window that looks like .
(It's the third button from the top.) Click it again. Each click
zoomed you out by a factor of two, so the chart is now 80 light-years
across, and it shows you stars within 40 light-years of the Sun.
(You can verify this by checking the value displayed for "Chart Radius"
under the CHART STATUS heading at the upper left of the display.)
You'll note that the red dwarfs, and even the Sun, have disappeared.
In fact, the only star still visible that was in the original chart
is Sirius, now near the center of the display. This is because
StarPlot tries not to clutter the chart
with too many stars at once, so by default it doesn't show dimmer
stars as you zoom out.

Your display will now look something like this. (You may be viewing
the chart from a completely different angle if you played with the
arrow buttons.) These are the brighter stars within 40 light-years:

What if you want to see all the dimmer stars that StarPlot isn't
showing you? You can do so by clicking the button that looks like
a number of times. (This button is the fifth from the top in
the newest version of StarPlot, or at the bottom in StarPlot version
0.95.4 or older.) With each click,
you will view stars one-half magnitude (a factor of 1.58 times) dimmer.
(Magnitudes are explained in the next
chapter if you aren't familiar with them.)
Go ahead and keep clicking it until the label "Dim Mag:" under the
CHART STATUS heading is immediately followed by the number 10.
(For now, ignore the second value in parentheses, if there is one.)
To make the chart
less cluttered, let's also get rid of those vertical reference bars
by selecting the menu option "Options->Toggle Bars".
The chart now looks like this, and clicking the same button more
will show you ever more dim red dwarfs if you like.

You may be interested in viewing a Hertzsprung-Russell (H-R) diagram of
these stars. If you don't know what this diagram is, check out
the next chapter, but basically it is a
scatter plot of star brightnesses (magnitude) against star
temperatures (spectral class). By convention, stars are brighter
(magnitude decreases)
going upward, and temperature decreases going toward the
right. To view the H-R diagram, select the menu option
"Stars->HR Diagram."
You will get a window that looks like the one shown below. Note
the gray horizontal bar near the bottom indicating the limiting
dim magnitude. While this window is displayed, you can continue
to make changes to the chart in the main window, and the H-R diagram
will automatically stay updated to show the stars currently displayed
on the chart.

Want to look at only the Sun-like stars in this region, which might
conceivably harbor Earth-like planets? This isn't too difficult.
Click on all the circles in the legend at the upper right of the
main StarPlot window to turn off
those types of stars, EXCEPT for the yellow and orange circles labeled
"G" and "K". (Your legend should now appear as shown at left.
If you've mistakenly clicked on the yellow or orange circle, click
on it again to toggle it back on.) This selects only stars of
temperature similar to the Sun.

Next, open up the "Chart->Star Filter" dialog box from the
menu. In the box for "Smallest (brightest) allowed magnitude,"
enter "3.5", and in the box for "Largest (dimmest) allowed magnitude,"
enter "7.0". Then click "OK." This selects only stars of brightness
similar to the Sun (whose absolute magnitude is about 4.8). Your
chart will now appear something like the one shown below. Note the
Sun at the center, and α (alpha) Centauri nearby.

To get information about these stars, select
Options->Star Labels->Numerical Index from the menu.
This will label stars with numerical indices instead of names, to
save space. Now, open up the star information dialog from the
menu option Stars->Chart Data. Voila—a display of
information for all the Sun-like stars within 40 light-years of us!
(Note that you can click on any of the column headers to sort the
stars by that column.) Like the HR diagram, this window will
be automatically updated any time you make changes in the main
chart window.

You can re-center the chart on a star other than the Sun if you like.
To demonstrate this, let's first undo all our changes that made us
see only Sun-like stars. Select the "Chart->Star Filter" menu
option, and in the dialog box that appears, click the "Revert" button
at bottom center. Also, select the menu option
"Options->Toggle Bars" followed by
"Options->Star Labels->Landmark Stars" to return to
the original appearance of the chart. This will give you back the
view seen in this image.

With the mouse, now left-click on the symbol (not the label) for
the star Arcturus. You have jumped to a different position;
the chart is centered on Arcturus and shows the bright stars within
40 light-years of Arcturus. If the Sun were visible, it would be
near the edge of the chart.

Another entertaining thing to do is to zoom in by a ridiculous amount.
Now that the chart is centered on Arcturus, keep pressing the "zoom in"
button (looking like ) until its
symbol begins to swell and fill most of the display. The
chart radius at this point is 2.38·10-6
light-years, or about 0.15 astronomical units (23 million kilometers).
Instead of
the star's brightness, the diameter of the symbol now represents
the actual diameter of the star at this scale. For an interesting
comparison, open the Chart->Define Chart dialog box,
type "Sun" into the star name entry box and click "Search." Then
hit "OK" to jump back to the Sun. You will see that the Sun is much
smaller in actual size than Arcturus is. In the graphic below,
for a direct comparison
the Sun has been superimposed at the lower right of the chart display
showing Arcturus.

0.3. Around the Galaxy

Let's now look at stellar structures on larger scales. The Gliese
catalog only includes stars within about 80 light-years of Earth,
so we must abandon it here. In the StarPlot main window, select
the "File->Open Star Database" menu option and choose the
file yale.stars or yale5.stars (whichever
exists on your system). If you wanted, you could keep the Gliese
catalog open as well by using the
"File->Merge Star Database" menu option to select the
Yale catalog instead, but
that might be confusing because the two files contain some of the
same stars, which would therefore be shown twice in slightly
different locations.

This tour could continue to take you through StarPlot
step-by-step just as above,
but now that you know something about the program that would be
tedious. Happily, StarPlot has the ability to save and load
"parameter files" containing all the information about the current
state of the program at any moment. So just copy the following
parameter files, which have already been set up for you, into
your home directory:

The first stop is the Hyades star cluster, the nearest star cluster
to Earth. This cluster consists of a few hundred stars that formed
from the same nebula, and over time have spread out over a
region about 50 light-years across. Just select the menu option
"File->Open Parameter File," and select the file
hyades.par that you earlier copied into your
home directory. The resulting view is shown below. In this case
the plane of the chart is shown in blue to indicate that you are
viewing it from below, to match the view of this star cluster we
actually see from Earth. The brightest star in the cluster is
Aldebaren, a red giant which is just left of center in this view.

Our next stop is the Scorpio-Centaurus Association, an extended
group of hot blue stars. Like the Hyades, these stars formed together,
but being less gravitationally bound to each other, they have
spread across hundreds of light-years. They make up most of
the stars that we see in the constellations of Scorpius, Centaurus,
and Crux in the southern sky. Open the scocen.par
parameter file using the "File->Open Parameter File"
menu option to obtain the chart shown below.

Finally, we look at a large fraction of the plane of our galaxy.
Open the galplane.par parameter file. What you see is
a selection of the brightest stars in the galaxy, making up part of
the galactic disk. The Galactic coordinate system is used in this
view so that the disk is in a horizontal plane within the chart.
(You can convert back to the "normal" celestial coordinate system
from the Options->Coordinate System submenu.)
Try clicking the button that looks like
a few times to view the Galactic disk edge-on and see just how
thin it is.
The center of our galaxy is toward the back of the chart, although it
is still well outside the volume of space shown.

This ends the tour of StarPlot. To learn more about stellar
astronomy and stars themselves, turn to the next
chapter. For a more thorough guide to StarPlot features,
start with Chapter 2.